Young couple goes on van tour of US, boy comes back with van - no girl

I just don't think Brian is clever enough to successfully flee the country. It is a lot harder than it used to be to not leave any digital footprints. And for the whole "boat to Cuba" thing you would have to already have a lot in place in advance. If you don't already own a boat in south Florida and have friends waiting for you in Cuba, it would be most difficult to buy/rent one without being witnessed, especially now with the media attention. He's just not that smart. Most likely hiding in the woods somewhere.

ETA: Eric Rudolph hid out for 6 years, but he was a pro survivalist and had all the time in the world to pre-arrange shelters and backup shelters long before anyone knew he was a suspect.